1) Field of the Invention
The present invention relates to a passive seat belt system of the type that an occupant-restraining webbing is moved between an occupant-restraining position and an occupant-releasing position automatically, for example, responsive to the opening or closure of a door arranged adjacent a seat to which the passive seat belt system is applied. Especially, this invention is concerned with a passive seat belt system having characteristic features in the structure of a limit switch for detecting the arrival of a movable anchor, to which the above webbing is fastened, at the occupant-restraining position or occupant-releasing position along a guide member to stop any further movement of the movable anchor. The present invention also relates to such a limit switch unit.
2) Description of the Related Art
Reference is first had to FIGS. 10-12, which illustrate by way of example parts of a companion passive seat belt system designed sometime ago except for certain details which are depicted in FIG. 12 and which pertain to the present invention. Illustrated in these drawings include a limit switch and a tube joint. The tube joint connects a cover tube--which serves to protect and guide a drive member for transmitting a drive force from a drive source to a movable anchor, such as a wire--to the side of a guide member for the movable anchor.
In these drawings, an anchor base 51 is arranged on a rear end portion of a rail 50 extending as a guide member along a center pillar of a vehicle body, namely, in the vicinity of an occupant-restraining position. The anchor base 51 is fixed on the side of the vehicle body by an anchor bolt 52. A latch mechanism 53 is disposed inside the anchor base 51. An anchor drive block 55 is fixed at a leading end portion of a drive wire 54. As the drive wire 54 is paid out, the anchor drive block 55 is brought into engagement with the movable anchor 56 so that the movable anchor 56 is dragged toward the occupant-restraining position. The movable anchor 56 is then latched by the latch mechanism 53, whereby the movable anchor 56 is stopped at the occupant-restraining position. When the movable anchor 56 is driven from the occupant-restraining position to the occupant-releasing position located frontward of the occupant-restraining position, the wire 54 moves upwards as viewed in FIG. 11 and, by a latch actuator block 55' disposed on the wire 54 at a position a little apart from the anchor drive block 55, the wire 54 begins to have the movable anchor 56 moved toward the occupant-releasing position while disengaging the latch mechanism 53 from the movable anchor 56 by the action of the latch actuator block 55'. These members are however not directly related to the present invention and their detailed description is omitted herein. For further details, reference may be had, for example, to U.S. Pat. No. 4,695,076 issued Sep. 22, 1987 to Toshiyuki Hane.
An emergency release buckle 57 is attached to the movable anchor 56. A tongue 64 carrying a webbing 63 fastened or otherwise connected at one end thereof to the tongue 64 is detachably inserted in and latched with the buckle 57. In the event of an emergency, the webbing 63 can be released from an occupant-restraining state by unlatching the tongue 64 from the buckle 57, thereby permitting the egress of an occupant. Further, the anchor bolt 52 is in engagement with the movable anchor 56 which is in the occupant-restraining position, whereby the anchor bolt 52 also serves to bear pulling forces applied to the movable anchor 56 from the webbing 63.
As shown in FIG. 11, a rear end switch 58 which detects the arrival of the movable anchor 56 at the occupant-restraining position and prevents any further movement of the wire 54 is disposed in a lower left-hand part of the anchor base 51, and a tube joint 59 discrete from the rear end switch 58 is attached to the rail 50 by a pin 60. The tube joint 59 receives and embraces a wire cover tube 61 and guides the wire 54 from an unillustrated drive means (e.g., motor) to the tube joint 59, and guides the wire 54 from the wire cover tube 61 into the rail 50.
In the companion passive seat belt system described above, the limit switch and tube joint are provided as discrete members, thereby involving the drawbacks that more components are required and more assembly steps are hence required.
Further, as illustrated in FIG. 11, the discrete rear end switch and tube joint are arranged side by side and the drive member, such as a wire, guided into the rail vertically extends through the anchor base. There is accordingly a limitation to any attempt of reducing the widthwise dimension of the anchor base. Although there is a recent trend toward narrower center pillars for use in motor vehicles, the above limitation makes it impossible to arrange an anchor base in such a narrow center pillar.